Equine Cushing’s disease, also known as pituitary pars intermedia insufficiency (PPID), is the most common endocrine disease diagnosed in horses.
Important points
- Cushing’s disease is a progressive disease of horses that affects the pituitary gland.
- Cushing’s disease in horses ends up causing the adrenal glands to produce more cortisol.
- Horses with Cushing’s disease may have underlying conditions such as equine metabolic syndrome.
- The treatment for Cushing’s disease in horses is an FDA-approved pill called Prascend® (pergolide).
What is Cushing’s disease in horses?
Cushing’s disease in horses is a progressive disease of the pituitary gland, a part of the endocrine system that plays an important role in producing and regulating hormones. Dysfunction of the endocrine system can have a negative impact on the horse’s entire body, causing immune and reproductive system dysfunction, coat deterioration, weight problems, and other symptoms discussed below.
Cushing’s disease in horses has the same name as Cushing’s disease. Although it is a similar disease that affects dogs and humans, the equine version affects different aspects of the pituitary gland. Cushing’s disease in dogs is caused by overproduction of cortisol (a stress hormone) in the adrenal glands, which are located just above the kidneys.
Effects of Cushing’s disease on horses
In horses, Cushing’s disease is usually seen in older animals when neurons in the brain’s hypothalamus, which produce dopamine, degenerate.
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Dopamine acts as a chemical messenger, telling other glands to increase or decrease the production of other hormones.
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When dopamine is depleted, the intermediate part of the pituitary gland becomes overactive and produces excess adrenocorticotropic hormone (ACTH), causing it to grow, much like a benign (non-cancerous) tumor.
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High levels of ACTH tell the adrenal glands to increase production of hormones such as cortisol.
All horse breeds can be diagnosed with Cushing’s disease, but pony and Morgan breeds may be predisposed to it.
Symptoms of Cushing’s disease in horses
Cushing’s disease is a progressive disease. Symptoms appear slowly but progress over time.
What are the first signs of Cushing’s disease in horses?
The onset of symptoms varies from horse to horse. Not all horses with PPID will develop all or most of these symptoms. The most common signs observed in horses with Cushing’s disease are:
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Winter coat does not fall out completely or falls out in patches
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long coat and/or curly coat
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behavioral changes
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Episodes of laminitis or multiple laminitis
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Hoof abscess or recurrent hoof abscess
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Infertility or lack of normal oestrus cycles in mares
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lethargy
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weight loss
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Accumulation of fat in abnormal areas
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top line loss
Late stages of Cushing’s disease in horses
Although some “common” early symptoms may also occur later in the disease in an individual horse, typical progressive symptoms of Cushing’s disease include:
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More pronounced muscle mass loss (especially in the back and hind legs)
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“Pot-bellied” appearance
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Increased water intake and urination
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excessive or inappropriate sweating
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repeated or chronic infections
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Abnormal mammary gland development
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suspensory ligament degeneration
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Recurrent corneal (eye) ulcers
What causes Cushing’s disease in horses?
Cushing’s disease in horses is a degenerative disease of the hypothalamus. The hypothalamus is a brain structure that controls hormone production through communication with the pituitary gland.
The endocrine system of a healthy horse is a balanced network of structures and organs that work together in a series of feedback loops to produce and regulate hormone levels throughout the body.
In horses with PPID, loss of function in the hypothalamus causes problems in an area of the pituitary gland called the pars intermedia (PI).
Cushing’s disease is a progressive disease. Symptoms appear slowly but eventually progress over time.
Normally, the pituitary gland produces hormones that help regulate normal body functions. Equine Cushing’s disease occurs when there is an abnormal growth (benign tumor) in the PI portion of the pituitary gland.
As the tumor grows, the PI also expands. This increases the production of a hormone called adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands to produce more of a hormone called cortisol.
Cortisol is known as the “stress hormone” and controls many important body functions, including blood sugar levels. Excessive and consistently elevated cortisol levels can lead to problems in horses, including increased susceptibility to infections, insulin resistance, laminitis, and muscle wasting.
Diagnosis of Cushing’s disease in horses
Veterinarians diagnose Cushing’s disease in horses using a combination of the horse’s medical history, physical examination, and diagnostic tests.
There are two main diagnostic tests for PPID. Baseline plasma ACTH concentrations and thyrotropin-releasing hormone (TRH) stimulation tests.
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of Baseline ACTH test This is a simple blood sample that your veterinarian sends to a laboratory.
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of TRH stimulation test This is also a blood sample, but requires two blood draws: a baseline sample and a second sample taken after the horse has been given a hormone called thyroid-stimulating hormone intravenously. A second blood sample is taken 10 minutes after the thyroid-stimulating hormone injection. Both samples are then sent to a lab and their ACTH levels are compared.
For early signs of Cushing’s disease in horses, a TRH stimulation test is recommended as the first test. In the early stages of the disease, baseline ACTH levels can be falsely negative.
In late stages of PPID, or in horses with multiple symptoms, baseline plasma ACTH level testing may be sufficient to make the diagnosis. Your veterinarian may require your horse to fast for 12 hours before blood is drawn.
Other tests recommended by your veterinarian include a nighttime dexamethasone suppression test and a magnetic resonance imaging (MRI) specifically for PI enlargement.
Treatment of Cushing’s disease in horses
There is no cure for PPID, but medications can be given daily to address the symptoms of the disease.
The first-line treatment for Cushing’s disease in horses is FDA-approved tablets. Prascend® (pergolide). Prascend® acts like synthetic dopamine and improves the control of ACTH production by Prascend®.
In some horses, Prascend® may need to be started gradually as it can cause a decrease in appetite.
Drug management of equine Cushing’s disease
Your veterinarian will likely recommend retesting your horse’s ACTH levels 1 to 3 months after medication and every 6 to 12 months thereafter.
Regular blood test monitoring is important to ensure that your Prascend® dose is effective and that your disease is not worsening. Some horses may require slightly higher doses over time as the disease progresses.
Recovery and management of Cushing’s disease in horses
Once your horse has been diagnosed with PPID and started on Prascend®, it is important to administer the medication as prescribed to help regulate ACTH levels. If levels fluctuate, symptoms may return.
Approximately one-third of horses with PPID also suffer from: It is a type of equine metabolic syndrome (EMS), so if your horse is suffering from both, he may need a low-sugar feed, dietary and exercise management, or other medications as directed by your veterinarian.
give a horse Cushing’s disease
Cushing’s disease does not affect all horses equally. Horses with PPID typically have an underlying medical condition such as equine metabolic syndrome or are sensitive to starch, so they will need a specific low non-structural carbohydrate diet or ration balancer that provides all the essential nutrients the horse needs. . With minimal calories.
Always consult your veterinarian to determine the appropriate diet for your horse on PPID or EMS. Depending on whether your horse is struggling with weight gain or loss and whether you have other metabolic concerns, you may need to increase or decrease the fat, carbohydrate, and protein content in your horse’s feed.
Horses that are or prone to insulin resistance and are on EMS may require strictly forage rations or pasture supplemented with a ration balancer.
Suitable feeds for horses that would benefit from a low NSC diet include:
Older horses that have difficulty maintaining weight may require a balanced geriatric diet, a high-calorie diet, or a fat supplement with no added carbohydrates.
Horses with PPID often have compromised immune systems, so supplementation with omegas and antioxidants may also be beneficial. Amino acids also help with topline loss.
What not to feed a horse with Cushing’s disease
Horses with Cushing’s disease usually should not be fed diets high in sugar. Grain must contain less than 10% sugar and starch, and analysis of horse hay may be required. If the sugar and starch levels in your hay are high, you may need to change your feed or soak your hay.
It is also recommended to limit grass intake, especially in spring and fall when grass sugar levels are highest.
Managing other symptoms of equine Cushing’s syndrome
In addition to treatment with Prascend® for PPID in horses, which often have a compromised immune system, regular Good wellness care is important. This includes:
Many horses with Cushing’s disease have a hard time shedding their coat in the winter. As temperatures rise, you can help your horse feel more comfortable. body clipping.
Frequently asked questions about Cushing’s disease in horses
How long does a horse live with Cushing’s disease?
Symptoms of Cushing’s disease in horses often occur after the age of 15. Medical management improves quality of life. It does not necessarily extend lifespan and depends on the horse’s overall health. Secondary symptoms that frequently occur in PPID, such as recurrent or severe laminitis and infections, can lead to systemic disease and early death.
What are the first signs of Cushing’s disease in horses?
Generally, the first clinical signs of Cushing’s disease are long hair or delayed shedding, abnormal fat deposits, loss of topline muscle, or weight loss and laminitis.
Is Cushing’s disease in horses terminal?
Horses cannot recover from Cushing’s disease, but with effective treatment, their symptoms can be managed and they can live a high quality of life.
What happens if my horse’s Cushing’s disease is left untreated?
If left untreated, Cushing’s disease will continue to progress and cause the horse’s weakened immune system to deteriorate. Secondary conditions such as laminitis may occur. Repeated or systemic infections can lead to other serious complications and decreased quality of life.
Is there a natural treatment for Cushing’s disease in horses?
Although there are no natural treatments that will cure Cushing’s disease or completely resolve the symptoms, you may want to discuss some alternative methods for treating PPID with your veterinarian. Chaste tree berry (monk pepper) is used in some horses with PPID because of its immune-stimulating properties. Complementary therapies such as chiropractic and acupuncture also support healthy immune function, hormonal balance, and nervous balance in the body.
